Cell phones, and smart phones in particular, are basically the most insecure and un-private creation of man. The first reason for this is the sheer amount of information gathering that your cell provider performs on your phone. Your cell provider knows basically everything that there is to know about you - where you go, who you call, who you associate with, how you spend your time. (This isn't even getting into GPS...) Cell towers can tell where your phone is within about 2000 feet, and the cell companies store this location data and other user metadata en masse. They give out your metadata to pretty much anyone who asks, including police, data brokers, and of course the National Spying Agency. The NSA has so many ways to mine this data that using a phone anonymously is basically impossible. They use location data and call metadata to find who interacts with a person, and then to find people who interact with those people, performing what they call 'hop analysis'. They can find people who use burner phones by analyzing the different phones' usage patterns and connecting the dots. Also, they watch for phones which are turned off for a while and then turned back on again, and they see which other phones were turned off for that period of time (looking for secret meetings).

There's no way to really use a phone without being subjected to this kind of surveillance. It is possible to encrypt your calls and messages, but usually this kind of encryption depends on the person that you are calling being able to decrypt the message by having some kind of software installed, and most people don't, or aren't willing to humour your paranoid delusions by installing some obscure, hard-to-use software client. And there's no way to hide your location from cell towers, so you're pretty much screwed anyway.

As though this isn't enough, the NSA and GCHQ allegedly have compromised a good part of the SIM encryption keys that are used to protect messages. The company that was compromised is called Gemalto. It is the largest SIM manufacturer in the world, and it makes about two billion SIM cards a year. Yes, two ****ing BILLION of these SIM cards have been compromised by the faggots. What this means is that the government no longer needs consent from the cell companies to intercept messages, they can simply sniff all of the cell traffic off of the air and decrypt it without anyone knowing. So if you thought that your stuff was secure because of that ****ty A5/1 or Kasumi crypto, then think again faggots..